
function tab(menuClassName,menuContClassName){
    // 定义变量来保存
    let menu=document.querySelectorAll(menuClassName)
let menuCont=document.querySelectorAll(menuContClassName)
    let index=0;
    menu.forEach(function(v,i){
      v.addEventListener('mouseover',function(){
        // console.log(a)
        // 进去之后先清空
        menu[index].classList=''
        this.classList='active'
        menuCont[index].classList='no'
        menuCont[i].classList='on'
        index=i;
      
      })
    })
    }
